Long term intraventricular cardiac assist devices are blood pumps that are surgically implanted within the diseased natural heart to support its function for extended periods of time. They must be miniaturized and must be extremely reliable. Blood pumps capable of this are disclosed in my U.S. Pat. No's. 4,994,078 and 5,092,879 entitled "Intraventricular Artificial Hearts and Methods of their Surgical Implantation and Use". Four-month animal survival with these devices is reported by Macris, et al., in the American Society of Artificial Organs Proceedings for 1994. Bearing durability in excess of twenty billion revolutions has been achieved in bench tests which represents about five years of pumping at 9,000 RPM. Wear measurements of bearings after five months' implantation in a calf indicate virtually no wear with projected bearing life in excess of 20 years. These findings prove that the intraventricular approach is likely to succeed.